Bob Johns (born 1942 in Lebanon, Indiana) is an American meteorologist specializing in severe convective storms and tornadoes. Johns spent his career in forecasting and forecaster training. Now retired, he is working on a project reanalyzing the Tri-State Tornado. He furthered forecasting techniques and developed the modern conceptualization of the derecho following landmark work on “northwest flow” severe weather patterns. Johns also introduced the enhanced wording "particularly dangerous situation" (PDS) to tornado watches for the 2 April 1982 tornado outbreak.[1]